Common use of Turbidity Clause in Contracts

Turbidity. Turbidity is a measurement of the water clarity. Turbidity is caused by sediment entering the water column and in some cases is caused but excessive nutrients causing algal growth. The threshold for turbidity is based on the EPA reference criteria identified in the document titled: Ambient Water Quality Criteria Recommendations Information Supporting the Development of State and Tribal Nutrient Criteria, Rivers and Streams in Nutrient Ecoregion VII. 2000. US Environmental Protection Agency. The values listed are specific to the appropriate sub- ecoregion identified in the document. Specific conductance is a measure of the drop-in voltage caused by the resistance of the water. Each stream tends to have a relatively constant range of conductivity. Significant changes in conductivity can be an indicator that a discharge or some other source of pollution has entered a stream. Nutrients are essential for growth. Streams often contain excessive levels of nutrients, which results in additional algae and other plant growth. The main nutrients of concern are phosphorus and nitrogen, and both elements can be found in several forms. Phosphorus can be measured as total phosphorus (TP) or ortho-phosphorus. Ortho-phosphorus typically represents the “reactive” and bioavailable form of phosphorus. Ortho-phosphorus can also be called Soluble Reactive Phosphorus depending on the analytical laboratory method used to quantify the amount of available phosphorus. Nitrogen can be measured as total nitrogen (TN), Kjeldahl nitrogen (TKN), nitrate+nitrite and ammonia nitrogen. TKN represents the fraction of TN that is unavailable for growth or bound up in organic form, it also includes ammonium. The remaining fractions, nitrate-nitrite and ammonia represent bioavailable forms of nitrogen. Phosphorus and nitrogen in excess amounts can accelerate eutrophication, causing dramatic increases in aquatic plant growth and changes in the types of plants and animals that live in the stream. This, in turn, affects dissolved oxygen, temperature and other indicators. Excess nitrates can cause hypoxia (low levels of dissolved oxygen) and can become toxic to warm-blooded animals at higher concentrations. The threshold values listed for nutrients are based on the EPA reference criteria identified in the document titled: Ambient Water Quality Criteria Recommendations Information Supporting the Development of State and Tribal Nutrient Criteria, Rivers and Streams in Nutrient Ecoregion VII. 2000. US Environmental Protection Agency. The values listed are specific to the appropriate sub-ecoregion identified in the document. In addition, the State of Wisconsin has passed a phosphorus rule that established a value of 0.075 mg/L of total phosphorus for most streams. Coliform bacteria are a commonly used indicator of the sanitary quality of foods and water. Coliforms are abundant in the feces of warm-blooded animals, but are also found in the aquatic environment, soil and on vegetation. While coliforms are themselves not normally causes of serious illness, they are easy to culture and their presence is used to indicate that other pathogenic organisms of fecal origin may be present. E. coli bacteria have been commonly found in recreational waters and their presence is used to indicate the presence of recent fecal contamination, but E. coli presence may not be indicative of human waste. E. coli are harbored in all warm-blooded animals, birds and mammals alike. E. coli bacteria have also been found in fish and turtles. The Nation analyzes bacteriological surface water samples using the IDEXX Colilert Quanti-tray enumeration method. Traditional membrane filtration tests for bacterial water quality generally count colonies of bacteria and report the value as colony forming units (CFU). The newer defined substrate tests, such as Colilert, report values as a most probable number (MPN). MPN is a statistical representation of what level of Total Coliforms or E.coli are likely present in a sample. For the purpose of this assessment, the terms CFU and MPN are used interchangeably. Threshold values for E.coli are based on NR102.04 (6) that states the geometric mean (126 counts per 100mL) shall not be exceeded in any rolling 90-day period during the recreation season. The statistical threshold value (410 counts per 100mL) shall not be exceeded more than 10% of the time during any rolling 90-day period during the recreation season. It should be noted that comparison of sample results to these threshold values is limited because of the small number of samples the Nation collects at any given sampling station. The percent exceedance listed in the table for each station is the comparison of sample results to the 410 colonies per 100mL threshold.

Turbidity. Turbidity is a measurement of the water clarity. Turbidity is caused by sediment entering the water column and in some cases is caused but excessive nutrients causing algal growth. The threshold for turbidity is based on the EPA reference criteria identified in the document titled: Ambient Water Quality Criteria Recommendations Information Supporting the Development of State and Tribal Nutrient Criteria, Rivers and Streams in Nutrient Ecoregion VII. 2000. US Environmental Protection Agency. The values listed are specific to the appropriate sub- ecoregion identified in the document. Specific conductance is a measure of the drop-drop in voltage caused by the resistance of the water. Each stream tends to have a relatively constant range of conductivity. Significant changes in conductivity can be an indicator that a discharge or some other source of pollution has entered a stream. Nutrients are essential for growth. Streams often contain excessive levels of nutrients, which results in additional algae and other plant growth. The main nutrients of concern are phosphorus and nitrogen, and both elements can be found in several forms. Phosphorus can be measured as total phosphorus (TP) or ortho-phosphorussoluble reactive phosphorus (SRP). Ortho-phosphorus SRP typically represents the “reactive” and bioavailable form of phosphorus. Ortho-phosphorus can SRP is also be called Soluble Reactive Phosphorus depending on the analytical laboratory method used to quantify the amount of available phosphorusorthophosphate. Nitrogen can be measured as total nitrogen (TN), Kjeldahl nitrogen (TKN), nitrate+nitrite and ammonia nitrogen. TKN represents the fraction of TN that is unavailable for growth or bound up in organic form, it also includes ammonium. The remaining fractions, nitrate-nitrite and ammonia represent bioavailable forms of nitrogen. Phosphorus and nitrogen in excess amounts can accelerate eutrophication, causing dramatic increases in aquatic plant growth and changes in the types of plants and animals that live in the stream. This, in turn, affects dissolved oxygen, temperature and other indicators. Excess nitrates can cause hypoxia (low levels of dissolved oxygen) and can become toxic to warm-blooded animals at higher concentrations. The threshold values listed for nutrients are based on the EPA reference criteria identified in the document titled: Ambient Water Quality Criteria Recommendations Information Supporting the Development of State and Tribal Nutrient Criteria, Rivers and Streams in Nutrient Ecoregion VII. 2000. US Environmental Protection Agency. The values listed are specific to the appropriate sub-ecoregion identified in the document. In addition, the State of Wisconsin has passed a phosphorus rule that established a value of 0.075 mg/L of total phosphorus for most streams. Coliform bacteria are a commonly used indicator of the sanitary quality of foods and water. Coliforms are abundant in the feces of warm-blooded animals, but are also found in the aquatic environment, soil and on vegetation. While coliforms are themselves not normally causes of serious illness, they are easy to culture and their presence is used to indicate that other pathogenic organisms of fecal origin may be present. E. coli bacteria have been commonly found in recreational waters and their presence is used to indicate the presence of recent fecal contamination, but E. coli presence may not be indicative of human waste. E. coli are harbored in all warm-blooded animals, birds and mammals alike. E. coli bacteria have also been found in fish and turtles. The Nation analyzes bacteriological surface water samples using the IDEXX Colilert Quanti-tray enumeration method. Traditional membrane filtration tests for bacterial water quality generally count colonies of bacteria and report the value as colony forming units (CFU). The newer defined substrate tests, such as Colilert, report values as a most probable number (MPN). MPN is a statistical representation of what level of Total Coliforms or E.coli are likely present in a sample. For the purpose of this assessment, the terms CFU and MPN are used interchangeably. Threshold values for E.coli are based on NR102.04 (6) that states the geometric mean (126 counts per 100mL) shall not be exceeded in any rolling 90-day period during the recreation season. The statistical threshold value (410 counts per 100mL) shall not be exceeded more than 10% of the time during any rolling 90-day period during the recreation season. It should be noted that comparison of sample results to these threshold values is limited because of the small number of samples the Nation collects at any given sampling station. The percent exceedance listed in the table for each station is the comparison of sample results to the 410 colonies per 100mL threshold.